In the past, near-field optical microscopes, such as those described in U.S. Pat. No. 4,604,520, have incorporated spectrophotometer in order to obtain information about the composition of the specimen being examined. However, they are plagued by the extremely slow rate at which the specimen area can be scanned. This problem has severely limited the use of near-field optical microscopes and spectrophotometer for commercially important applications in the biological and industrial fields. In addition, near-field optical microscopes can not achieve the resolution of scanning probe microscopes.
On the other hand conventional scanning probe microscopes, such as scanning tunneling microscopes and atomic force microscopes, have been able to make only limited determinations of the constituents of an object under inspection. Moreover, these conventional scanning probe microscopes cannot define the structure of the object below its surface and cannot define with fine resolution pits, walls, projections, and other structures which prevent the end of the probe tip from coming close enough to the object in these areas for accurate inspection by conventional scanning probe microscopy.
U.S. Pat. No. 5,319,977 describes a scanning probe microscope that utilizes the probe tip to make acoustic microscopy measurements and either atomic force microscopy (AFM) measurements or scanning tunneling microscopy (STM) measurements during the same scanning sequence. The resolution of acoustic microscopy is however rather low in comparison to AFM, STM, or near-field optical microscopy. Moreover, as with conventional scanning probe microscopes, the scanning probe microscope described in U.S. Pat. No. 5,319,977 cannot define those types of structures which prevent the end of the probe tip from coming close enough to the object for accurate inspection.
Furthermore, many objects exhibit areas of varying composition and conductivity. For example, the surface of a semiconductor may change from being conductive to insulative as a function of position. However, no scanning probe microscopes currently exist which are capable of making STM, AFM, near-field optical microscopy, and spectrophotometric measurements during the same scanning sequence in order to properly image and identify such an object.